Why don't Python tooltips appear for the 'Median' transform values in Edit mode?
Those attributes are not completely using RNA API in its source code

TL;DL What is this DNA and RNA stuff?
RNA is also something that is partially made by code generation, using code in source/blender/makesrna. It is supposed to be a somewhat more abstract and nicer interface to the DNA data. For example, where a DNA struct might use a particular bit in a short for some flag, RNA would expose that as a bool property. So far, this nicer Data API isn't used too much in the C source code. Where it is heavily used is as the interface to and from Python. Most of the Python access to Blender data is generated automatically to use the RNA system. See Source/Architecture/RNA for more information about RNA.

The source of edit mode transform is in source &gt; Blender &gt; editors &gt; space_view3d &gt; view3d_buttons.c::code line 560. Which doesn't seems to provide RNA API for more button information.
Another example from object mode transform, the proper RNA definition is in source &gt; blender &gt; makesrna &gt; intern &gt; rna_object.c :: line code 2740 with the following code:
  /* transform */
  prop = RNA_def_property(srna, &quot;location&quot;, PROP_FLOAT, PROP_TRANSLATION);
  RNA_def_property_float_sdna(prop, NULL, &quot;loc&quot;);
  RNA_def_property_editable_array_func(prop, &quot;rna_Object_location_editable&quot;);
  RNA_def_property_ui_text(prop, &quot;Location&quot;, &quot;Location of the object&quot;);
  RNA_def_property_ui_range(prop, -FLT_MAX, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
  RNA_def_property_update(prop, NC_OBJECT | ND_TRANSFORM, &quot;rna_Object_internal_update&quot;);

Which make those button reveal python tooltip automatically .